For myself I can just feel it. Arthritic pain etc. When I eat a lot of anything containing wheat. Pizza for one. My left ankle will swell up painfully for a week sometimes. I still have pizza from time to time. But I know I will suffer for it.

I did however go to a rheumatologist a couple years ago and get a blood test to discover what was causing me issues yes. Since then I’ve generally gone on a more keto diet. With lots of fruits and vegetables which I don’t react to. But mainly cutting out as much of the processed foods and trouble foods as I can.